Development of a peroral, droplet-dose bioassay laboratory technique and its application on a granulovirus for Thaumatotibia leucotreta (Lepidoptera: Tortricidae)

摘要

The false codling moth, Thaumatotibia (= Crypto-phlebia) leucotreta Meyrick (1912) (Lepidoptera: Tortricidae) is regarded as a serious pest on citrus and other crops in Africa south of the Sahara (Newton 1998). Biological pesticides have been formulated using entomopathogenic viruses such as granuloviruses (Baculoviridae) (Hunter-Fujita et al. 1998). The efficacy of registered biological control formulations using naturally-occurring South African Cryptophlebia leucotreta granulovirus (CrleGV-SA) needs to be determined as close to field conditions as possible. This is necessary as T. leucotreta eggs are laid on the surface of the fruit and CrleGV-SA biopesticides target the neonate larvae before they burrow into the fruit, where they remain until pupation (Newton 1998). Therefore there is only one chance for larvae to ingest virus (Lacey 1997). An understanding of these pathogen-host interactions and an ability to measure these properties is needed for the selection of effective isolates and formulations (Hughes et al. 1986). There is a need to quantify and monitor the potency of preparations accurately (Hughes et al. 1986). Due to its precision, the peroral droplet technique is widely used for determining the lethal dose of baculoviruses (Bouwer& Avyidi 2006; Kunimi & Fuxa 1996; Smits & Vlak 1988).